This application claims the benefit of the Korean Application Nos. P2002-21231, and P2002-21232, both filed on Apr. 18, 2002, which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a magnetron having an improved self-cooling performance.
2. Background of the Related Art
In general, the magnetron has applications in microwave ovens, plasma lighting fixtures, dryers, and other microwave systems.
The magnetron, a kind of vacuum tube, emits a thermal electron from a cathode thereof as a power is applied thereto, and the thermal electron emits a microwave by action of strong electric, and magnetic fields. The microwave is forwarded through an antenna, or a feeder, and used as a heat source for heating an object.
In general, the magnetron is provided with an oscillating part and a magnetic circuit part for generating the microwave, an input part for receiving and providing a power to the oscillating part, an output part for forwarding the microwave generated by the oscillating part and the magnetic circuit part, and a cooling part for cooling the magnetron, of which detailed system will be described with reference to FIG. 1. FIG. 1 illustrates a related art magnetron.
Referring to FIG. 1, there are elements of the input and output parts in upper and lower parts of a yoke 1 which forms a magnetic closed circuit as a part of the magnetic circuit part, and there are elements of the oscillating part and the magnetic circuit part inside of the yoke 1.
The oscillating part has an anode 11 and a cathode 16. As shown in FIG. 1, the anode 1 is cylinder fitted to a center of the yoke 1. On an inside surface of the anode 11, there are a plurality of vanes 15 fitted in a radial direction toward a center of the anode 11, to form a interaction space 15a at the center of the anode 11 the vanes 15 and spaces between the vanes 15 inside of the anode 11 form resonance cavities. There is a cathode 16 of a filament fitted in the interaction space 15a, with a center lead 17a and a side lead 17b for receiving a power.
The magnetic circuit part is provided with one pair of magnets 12a and 12b, one pair of magnetic poles 13a and 13b, and a yoke 1. As shown in FIG. 1, there is one pair of magnets 12a and 12b; an upper magnet 12a over the anode 11 and a lower magnet 12b under the anode 11. Both the upper magnet 12a and a lower magnet 12b are hollow, each for leading an antenna feeder 32, a center lead 17a, and a side lead 17b to outward. There are also one pair of magnetic poles 13a and 13b; an upper magnetic pole 13a between an upper side of the anode 11 and the upper magnet 12, and a lower magnetic pole 13b between a lower side of the anode 11 and a lower magnet 12b. The upper magnetic pole 13a and the lower magnetic pole 13b is fitted perpendicular to axes of the anode 11 and the cathode 16. The yoke 1 has a yoke upper plate 1a and a yoke lower plate 1b, which are joined together to form the magnetic closed circuit.
In the meantime, for keeping an air tightness and vacuum of the inside space of the magnetron, the magnetron is provided with components, such as an A seal 14a, F seal 14b, an upper end shield 18a, and a lower end shield. The A seal 14a, and the F seal 14b of cylindrical metal containers are fitted between a top part of the anode 11 and the output part, and a bottom part of the anode 11 and the input part, for maintaining sealing. For fitting the A seal 14a and the F seal 14b as shown in FIG. 1, it is required that the upper magnet 12a and the lower magnet 12b are inserted to outer circumferential surfaces of the A seal 14a and the F seal 14b respectively. An opened bottom part of the F seal 14b is closed by a ceramic stem 21. As shown in FIG. 1, the upper end shield 18a and the lower end shield 18b are also fitted to top and bottom ends of the cathode 16.
The input part has a condenser 23 and a choke coil 23a. For preventing leakage of the microwave from the oscillating part, and protecting the choke coil 23a and a ceramic system 21, there is a filter box 22 fitted under the yoke 1 where the input part is fitted. There is a condenser 23 at one side of the filter box 22, and the choke coil 23a is fitted inside of the filter box 22 so as to be connected with the condenser 23. There are one pair of external connection leads 23b from the choke coil 23a, passed through a ceramic system 21 and connected to the center lead 17a and the side lead 17b. 
The output part has an antenna feeder 32, an A ceramic 31, an antenna cap 33. The antenna feeder 32 has one end connected to the vane 15, and the other end extended trough the magnet 12 to an outer upper side of the yoke 1. As shown in FIG. 1, the A fitted to top of the A seal 14a, and the antenna cap 33 is on the A ceramic 31, surrounding an end of the antenna feeder 32.
The cooling part 34 has cooling fins 34 and a cooling fan (not shown). The cooling fin 34 has one end connected to an outside surface of the anode 11, and the other end connected to an inside surface of the yoke 1. The cooling fan is fitted to an outside of the yoke 1 for blowing external air toward the yoke 1. To do this, there are an inlet (not shown) and an outlet (not shown) in an outside case (not shown) of the magnetron for drawing and discharging the external air therethrough by using the cooling fan.
The operation of the magnetron will be described.
When power is provided to the oscillating part through the input part, thermal electrons are emitted from the cathode 16 to the interaction space 15a, where a magnetic field formed by one pair of the magnets 12a and 12b is focused through the one pair of magnetic poles 13a and 13b. According to this, the thermal electrons in the interaction space 15a are made to circulate by the magnetic field, such that the microwave is generated as oscillation of the thermal electrons is kept excited as the thermal electrons are synchronized to the resonance spaces of the anode 11.
The microwave generated thus is transmitted through the antenna feeder 32 extended from the vane 15 to an outside, and emitted to outside through the A ceramic 31 and the antenna cap 33. The microwave emitted to outside of the magnetron cooks or warms up food when the magnetron is applied to a microwave oven, and emits light by exciting plasma when the magnetron is applied to lighting fixtures or the like.
In the meantime, a microwave energy which fails in emission to outside of the anode 11 after being generated in the oscillating part is dissipated as heat, which is dissipated by the cooling fin 34 and the cooling fan to outside of the anode 11. That is, the heat is transmitted from the anode 11 to the yoke 1 through the plurality of cooling fins 34, and the heat transmitted to the yoke 1 is heat exchanged with external air blown by the cooling fan, to dissipate the heat and cool down the magnetron.
However, not all the heat from the anode 11 is dissipated through the cooling fin 34 and the cooling fan, but a portion thereof is transmitted to the magnets 12a and 12b adjacent thereto. Because the magnets 12a and 12b on a direct heat transmission path from the anode 11 have no other heat dissipation path, the magnets 12a and 12b are involved in heating to a temperature similar to the anode 11. The long time exposure of the magnets 12a and 12b to a high temperature affects an intensity of the magnetic field and the magnetic circuit, which cause power drift of the magnetron.
When the magnetron is cooled down with the cooling fan, the cooling fan generates noise and vibration when in operation, and the cooling fan requires a fitting space, that makes the magnetron larger.
The outside case requires the inlet and the outlet for introduction and discharge of the external air to/from the outside case. If the magnetron is applied to a product to be disposed in outdoor such as a light fixture, the inlet/outlet in the outside case may allow rain, dusts, and insects to enter therein, which may cause operative problem and frequent trouble of the magnetron.
Accordingly, the present invention is directed to a magnetron that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an excellent air cooling type magnetron in which heat dissipation paths of an anode and magnets are formed together.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the magnetron includes a cylindrical anode having a resonant space formed therein and a cathode fitted therein, magnets fitted to upper and lower sides of the anode, a yoke fitted on outsides of the anode and the magnets to form a closed circuit, and cooling devices including a main cooling device to form a heat discharge path from the anode, and a supplementary cooling device to form a heat discharge path from the magnet direct or indirectly.
The main cooling device is an anode heat conductor having one end closely fitted to an outside surface of the anode, and the other end passed to the yoke and exposed to an external air.
The supplementary cooling device includes a magnet heat conductor closely fitted to an outside surface of the magnet, having one side in contact with the outside case of the magnetron, a yoke heat conductor closely fitted to an outside surface of a yoke plate, the yoke heat conductor having one side in contact with the outside case of the magnetron, or a magnet heat conductor closely fitted to an outside surface of the magnet, the magnet heat conductor having one side in contact with the outside case of the magnetron, and a yoke heat conductor closely fitted to an outside surface of a yoke plate, the yoke heat conductor having one side in contact with the outside case of the magnetron.
The anode heat conductor includes a head closely fitted to an outside surface of the anode, an extension from the head to pass through the yoke, and a heat dissipation plate connected to an outside end of the extension and exposed to external air, or a head closely fitted to an outside surface of the anode, a heat pipe having one end closely fitted to the head, and the other end passed through the yoke to be positioned at an exterior, and a heat dissipation plate connected to an outside end of the heat pipe and exposed to external air. Both ends of the heat pipe are inserted in the head and the heat dissipation plate, respectively.
The head includes at least two members for detachably fitting to surround an outside surface of the anode.
The magnetron further includes a heat transmission material applied to a part the outside surface of the anode is in contact with the head. The heat transmission material is a grease, or a paste.
The heat dissipation plate includes a plurality of heat dissipation fins fitted thereto. The heat dissipation fin is a thin and long plate.
The heat dissipation plate forms one face of the outside case. The heat dissipation fin is a thin and long plate fitted to an outside surface of the outside case.
The magnetron further including insulating members fitted between both ends of the anode and the magnets, and between the magnets and the yoke.
The insulating member is formed of mica or asbestos, in a form of a disk or polygonal plate having a hole in a central part.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.